Low-torque stepper switch



1956 E. R. STODDARD ETAL 3,233,066

LOW-TORQUE STEPPER SWITCH Filed Feb. 26, 1963 3 Sheets-Sheet 1 INVENTORS ERNEST R. STODDARD SINCLAIR N. SUTHERLAND ATTO R N EYS Feb. 1, 1966 Filed Feb. 26, 1963 E. R. STODDARD ETAL LOW-TORQUE STEPPER SWITCH FIG.2

s Sheets-Shet 2 nuun SELECT WETTNT l l l- INVENTOR ERNEST R. STODDARD SINCLAIR N. SUTHERLAND WWW LOW-TORQUE STEPPER SWITCH 3 Sheets-Sheet 5 Filed Feb. 26, 1963 PIC-3.3

62 INVENTOR.

ERNEST R. STODDARD SINCLAIR N. SUTHERLAND BY 32 W/JMQ) ATTORNEYS United States Patent 3,233,066 LOW-TORQUE STEPPER SWITCH Ernest R. Stoddard, Wolcott, and Sinclair N. Sutherland,

New Haven, Conn, assignors to Consolidated Electronics Industries Corp., Waterbury, Conrn, a corporation of Delaware Filed Feb. 26, 1963, Ser. No. 261,013 Claims. (Cl. 200105) This invention relates to rotary switches of the type having a stepper motor, a rotary switch arm and a plurality of switch contacts, and more particularly to a new and improved printed circuit, stepping switch unit having minimal torque requirements and a small, lowtorque motor for driving the rotary switch arm.

Conventional stepper switches have require-cl larger motors 10f comparatively high torque to overcome the loads present, both mechanical and electrical, during stepping. This shortcoming of conventional rotary switches, especially prevalent in those used for multiple circuit switching operations, has been eliminated by the new and improved rotary stepping switch unit disclosed herein. Specifically, the new rotary switch unit, incorporating the principles of the present invention, is characterized by the substantial reduction or the removal of electrical and mechanical loads from its rotary switch arm; hence, from the motor shaft, during stepping. This is accomplished by using a self-biasing rotary contact arm which normally maintains itself out of physical contact with the switch contacts during stepping. The switch arm is moved into and held in physical contact with a selected fixed contact, after stepping, by extrinsic means in the form of a novel switch hand which is advantageously actuated through an electromagnetic clutch.

More specifically, the rotary stepping switch unit of the invention includes first and second switch decks and a clutch deck, all of which are held in a mutual, spaced relation by several deck posts. A small, low-torque, stepper motor for indexing a pair of rotary arms about the faces of the switch decks is mounted on the rear surface of the first switch deck. Twenty-two individual printed circuits, each having a printed commutator contact, and an associated printed slip ring, are included on the front surface of the first deck. Also included on the front surface of the first deck, and constituting an important specific aspect of the invention, is a printed homing switch adapted to home the stepper motor to one of two predetermined home positions.

The second switch deck has twenty printed circuits, each of which has a printed switch contact, and an associated printed slip ring. Also associated with each of these switch contacts is a resilient switch finger, carried by a non-rotatable switch hand which is axially movable by means of an electromagnetic clutch mounted on the third deck to move all of the fingers into and out of contact with their associated printed switch contacts.

The stepper motor shaft is projected through the switch decks and carries first and second rotary arms which cooperate with printed circuits on the first and second switch decks, respectively, to perform predetermined switching operations. The first, a rotary brush arm, carries two pairs of brushes, one pair of which is adapted to connect selectively and electrically each of the twenty two printed commutator contacts with the printed slip ring. The other pair of brushes, in cooperation with the new printed homing circuit, acts as a homing switch to move the stepper motor to a predetermined home position when the motor is energized through the homing switch.

Each of the twenty-two commutator contacts on the first switch deck, in cooperation with its associated brushes and slip ring, thus functions as a single-pole, single-throw 3,233,066 Patented Feb. 1, 1966 switch, which is normally open. The homing circuit, with its associated brushes, functions as a single-pole, single-throw switch, which is normally closed.

The second arm, a rotary switch arm, movable between commutator contacts and fingers of the conductive hand, is in the form of a resilient leaf spring which is crimped and pre-strcssed so as to be normally out of physical contact with the switch contacts on the second deck as the switch arm is selectively indexed by the stepper. Physical contact is established only after completion of indexing and actuation of the conductive hand. The absence of physical contact during stepping significantly reduces the mechanical loads on the stepper motor, permitting the use of an extremely low-torque motor to index the rotary arms, and also prevents make-and-break electrical contact as the arm is advanced.

In accordance with the invention, the rotary switch arm is selectively rotated, while out of contact with the switch contacts, to a selected switch contact. During this switch selection, the switch arm is also maintained free from contact with the switch hand. After the switch selection has been made and the stopper motor de-energized, the electromagnetic clutch is energized to cause the switch hand to move the switch fingers toward the switch contacts. As the fingers approach the contacts, the finger above the selected contact will press against the resilient switch arm, through an insulator associated with the arm, to move the crimped portion of the switch arm into contact with the selected switch contact. The switch hand, having a separate radial finger for each fixed contact, shorts out the remaining nineteen, non-selected circuits and connects them in common to its own electrical circuit, while the switch arm electrically connects the selected switch contact to the slip ring. Thus, each of the twenty, second deck switch contacts generally functions as a sin gle-pole, double-throw switch.

The new and improved lowtorque, stepper switch unit is especially advantageous in conventional multiple switching applications, such as in telephone and intercommunication systems, that have heretofore required hightorque motors to overcome the relatively large mechanical loads imposed thereupon by conventional contact arrangements requiring a contact arm to be moved between two non-rotating contact elements. Thus, the novel stepper switch unit disclosed herein may be used to extreme advantage in selective switching operations in which the non-selected switches are to be shorted out to a separate input.

The new stepper switch unit also includes novel circuit features providing two home positions. The homing circuit arrangements have been found especially well suited for dial intercom telephone applications and the like.

For a better understanding of the invention, reference should be had to the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side elevational view of a rotary stepping switch embodying the principles of the present invention;

FIG. 2 is a cross-sectional view of the mechanism of FIG. 1 taken along line 2r2 thereof, with parts broken away to show details of construction;

FIG. 3 is a cross-sectional view of the mechanism of FIG. 1 taken along line 33 thereof, with parts broken away to show details of construction;

FIG. 4 is an enlarged fragmentary front elevational view of the rotary switch arm of the mechanism of FIG. 1;

FIG. 5 is a fragmentary side elevational view of the rotary switch arm of FIG. 4 in an active position; and

FIG. 6 is a fragmentary side elevational view of the 3 crimped portion of the switch arm of FIG. 4 in an active position during indexing of the stepper motor.

With reference to FIG. 1, the rotary stepper switch unit of the present invention is indicated generally by numeral and comprises, generally, first and second switch decks 11 and 12, a stepper motor 13, an electromagnetic clutch indicated generally by numeral 14, first and second rotary arms 15 and 16 and a switch hand 17.

The first switch deck 11 includes, on its front surface, a series of printed circuit branches A-W, each of which circuit branches A-W terminates at a printed commutator bar 18. These printed commutators are disposed in two semi-circular patterns about the stepper motor shaft 19. Adjacent commutator bars in each pattern are separated by an angular displacement of approximately fifteen degrees and the two semi-circular commutator bar patterns, themselves, are separated from one another by blank, diametrically opposed spaces Zil, 21, which spaces shall be hereinafter designated respectively as first and second home positions. A printed slip ring 22 is located concentrically within the generally circular outline formed by the semi-circular patterns of commutator elements 18, and these printed commutator elements 18, along with the printed slip ring 22, form the contacts for a series of single-pole, single-throw switches.

Located concentrically within the printed slip ring 22 is a printed homing circuit 23, which is completely discontinuous in the area of the first home position 2%) and offset in the area of the second home position 21. In accordance with the present invention, a step-through printed contact 24- is located in the general area of the second home position 21 within the circular outline of the home circuit 23, and a homing slip ring 25, in the form of an endless loop, is located concentrically within the generally circular outline of home circuit 23. The printed homing circuit elements 23-25 constitute a novel homing switch, the operation of which will be described in greater detail hereinafter.

The first switch deck 11 also includes, on its face, printed leads 26, 27, 24a and 28, which are adapted to supply appropriate electrical inputs to the printed circuit elements 22, 23, 24 and 25, respectively. As shown in FIG. 2, the printed lead 24a is linked to the printed circuit 24 by a jump Wire 2412. In addition, printed circuit leads 29, 30, and 31 are provided to supply a pulsating D.C. input alternately to each half of a center-tapped coil of the stepper motor 13.

With reference to FIG. 3, the front face of the second switch deck 12 includes printed circuit branches a-t, each of which terminates at a printed switch contact 32. The printed switch contacts 32 are disposed in two semicircular patterns about an auxiliary drive shaft 19a and are also spaced from one another at approximate fifteen degree intervals. The two semi-circular patterns of switch contacts 32 are separated from one another by two, thirty-degree intervals which are generally aligned with the first and second home positions of the first switch deck. Located within the circular outline of the switch contacts 32 is a second printed slip ring 23, whose electrical input is supplied by a printed lead 34. In accordance with the invention, the printed switch contacts 32 and the printed slip ring 33 constitute essential elements of a series of single-pole, double-throw switches.

The stepper motor 13 is adapted to have each half of its center-tapped coil alternately energized by a series of direct current pulses. Each alternation of polarity is adapted to index the motor rotor one pole position. Advantageously, the stepper motor 13 is a 24-pole motor, so that with each subsequent pulse, its rotor advances or indexes a single, fifteen degree increment. Advantageously, the motor 13 is self-starting and unidirectional, for example, in the counterclockwise direction, as illustrated. A motor of this general type is more fully and completely described in the copending application Serial No. 19,958 of William Riggs, filed April 4, 1960.

The stepper motor 13 is mounted on the rear surface of switch deck 11 by a series of screws 35 and spacers 36, in such manner that the rotor shaft 19 projects through the switch deck 11 and beyond the front surface thereof. Coupled with the rotor shaft 113 by a hub 38 is an auxiliary drive shaft 19:: which projects through the switch deck 12. The rotor shaft 19 carries the rotary brush arm 15 in the form of an insulating brush block 37, which block is adapted to drive the auxiliary shaft 19a through the hub 38 by a drive pin 33a. In addition, the brush block 37 carries brush elements 39, 40, each of which defines a pair of brushes 41, 41a and 42, 42a, respectively, which are held in contact with the face of the switch deck 11. The use of drive pin connected shafts 19, 19a facilitates modular construction of the complete unit and also avoids binding in case of misalignment of the decks.

The rotary switch arm 16 is best illustrated in FIGS. 46 and comprises a resilient, conductive leaf spring 43 having a crimped end portion 44 and a flexible insulator arm 45 carried on the top surface thereof. Advantageously, the insulator arm 45 and leaf spring 43 are held together as a single unit by bent ears 46 of the leaf spring and an insulating washer 46a as shown in FIG. 4. In accordance with the invention, the rotary switch arm 16 is fixed to the auxiliary shaft 19:: in such manner that the crimped end portion 44 is in close proximity to, but not in contact with, the printed switch contact elements 32 on the face of the switch deck 12, as shown in FIG. 6.

Four supporting posts 47 and screws 49 maintain the switch decks 1:1 and 12 in a predetermined mutual spaced relation and also support a clutch deck 48 in a spaced relation from the switch deck 12. Mounted on the rear surface of the clutch deck 48 is an electromagnet 50, which houses a clutch coil 51 and has an armature 52 normally biased outwardly therefrom by a spring 53. In accordance with the invention, the armature 52 is secured to the end of an axially movable clutch shaft 54 by riveting, and is supported in a bearing 54a. As shown in FIG. 3, two coil-energizing lead wires 5f connect the coil '51 with the printed leads 57 (FIG. 3).

The inner end of the clutch shaft 54 mounts a hub 58, which hub carries an insulating disk 59. As best illustrated in FIG. 3, the insulating disk 59 has the springlike contact hand 17 secured thereto by rivets 60. In accordance with the invention, the spring hand 17 is made from a conductive, resilient material and includes a circular body portion 61 having a plurality of twintined resilient spring fingers 6-2 extending radially outward and forward therefrom. Each of the fingers has a curved end portion maintained adjacent to an associated with one of the printed switch contact elements 32. In the general projected area of the home positions, the spring hand '17 has a guide arm 63 having a slot 64 therein and a terminal arm d5. As best shown in FIG. 1, the slot '64 cooperates with a guide rod 66, mounted on the deck 12, to maintain the spring hand 17 nonrotataible with respect to the switch contacts 32 and to guide the switch hand in its axial movement. The terminal arm 65 is connected by a pair of freely flexible wires 67 to the pginted leads 68 on the surface of the second switch deck The stepping switch unit of the present invention may be operated as follows:

The stepper motor is operated by alternately energizing both halves of its coil by a source of DC. pulses. As stated hereinabove, each alternation of polarity causes the rotor shaft to index one pole or fifteen degrees in accordance with well known motor principles. Thus, by selecting the number of pulses with which the motor 13 is to energized, the angular rotation of the rotor shaft can be precisely controlled. For example, if it is desired to complete the circuit F on switch deck 11 and the circuit f on switch deck 12, the stepper motor 13 may be enengized with six pulses to advance the rotor shaft 19 and the auxiliary drive shaft 19a from the home position 20 counterclockwise (as viewed in FIGS. 2 and 3) ninety degrees. This will index the rotary arms 15, 16 to coin cident positions with the printed switch contact 32 and the printed commutator bar 18 associated with the selected circuits F, f.

While the stepper motor is energized by the selected pulsating input, the brush 41a will wipe the printed slip ring 22, which is connected to an electrical source XX, and the brush 4 1 will wipe the consecutive printed commutator elements associated with circuit branches A-E. The brushes 41, 41a, therefore, make and break the circuits A-E before connecting the selected circuit F to the source XX. However, the circuits a-e on the second switch deck 12 will remain open during the stepping of the motor 13 due to the resiliency of the leaf spring 43, which maintains the crimped end portion 44 out of contact with the switch contacts 32.

During the energization of the stepper motor to index the rotary switch arms to their selected positions, the electromagnetic clutch .14 is de-ener-gized allowing the shaft 54 to be urged rearwardly by the spring 53 acting against the armature 52. Upon the completion of the indexing of the switch arms by the stepper motor, the coil 51 or the electromagnetic clutch 14 will be enengized to move the armature 52 forwardly toward the coil 51, thereby causing the switch hand 17 to be moved toward the switch deck d2. Movement of the switch hand will cause the spring fingers to short out all of the nonselected circuits to an electrical source ZZ through the switch hand terminal arm 65, the wires 67 and the printed leads 68.

The selected circuit f will be electrically connected to an electrical source YY by means of the resilient crimped end port-ion 44 of the second rotary switch arm which will be urged against printed switch contact 32 by the switch hand 17. The insulator 45 prevents electric contact and potential shorting between the resilient spring 43 and the switch hand -17.

Thus, it is seen that a selective input, in terms of a predetermined number of pulses to the stepper motor 13, will result inthe connection of a selected circuit on the switch deck 12 to a source YY, the shorting of the remaining, nonselected, circuits of the deck 12 to a source ZZ, and the connection of a selected circuit on the first switch deck .11 to a source XX.

The homing aspects of the invention are best described by way of typical application in a two-digit telephone or interco-mimunication system, wherein it may be desirable to make a first circuit selection and then a subsequent second circuit selection, or just a first circuit selection alone.

In such an application, certain switching, external of the rotary switch unit itself, is necessary in order that the stepper motor be driven by the pulsing input through the printed homing circuit. Thus, when the stepper motor is energized through the printed slip ring 25 and the printed homing circuit 23, the brushes 42a, 42, associated respectively therewith, will complete the circuit therebetween. Therefore, the motor will be continually pulsed, and accordingly indexed, while the rotary :brush arm 15 is in any position other than the home positions 20, 21. That is to say, it the rotary brush arm 15 is at some point between circuits A-L, the motor will be continually pulsed until the brush 42a reaches the substantial discontin-uity (oil-set) in the circularity of the printed homing circuit 23 at the home position 21. At that position, the brush 42a loses contact wth the printed circuit 22. The motor will no longer be energized and the rotary arms 15, 16 and the motor 13 will be said to have horned in the second home position. It the rotary brush arm 15 had been between the circuits MW, the motor -13 wouldhave been pulsed until the brushes reached the discontinuity in the printed circuit 23 at the home position 20 and would have horned in the first home position.

This type of two-position homing is often necessary when two separate switch selections are to be made consecutively from each of the home positions, for example, when a two-digit telephone number is dialed. However, where a one-digit number is selected, homing to the first home position would not be accomplished as outlined above, due to the fact that the brush 42a would stop at the substantial discontinuity in the printed homing circuit 23 which coincides with the second home position 21.

To increase the utility of the rotary stepper switch unit and to enable its rotary arms to :be homed to the first home position after only one switch selection has been made, a step-through contact 24 advantageously is incorporated with the homing circuit 23. By appropriate external switching, the step-through printer contact 24, which is located at the substantial discontinuity in the printed circuit 23 in the area of the second home position, may be connected with the input to the printed circuit 23, by short circuiting the step-through contact 24 thereto. This contact 24 allows the motor to receive a pulse of long enough duration to one-half of its center-tapped coil to drive the motor for one, fifteen degree increment where it will then be in the appropriate position to receive a pulse to the other one-half of its coil. Thus, the motor may be energized through the step-through contact 24, although the brush 42a is in the area of the substantial discontinuity at the second home position 21.

Operation of the step-through contact 24 may be more fully explained by way of a description of a typical application in which a one-digit o two-digit telephone number may be selected. A highly simplified schematic representation of such a typical application is shown in FIG. 2. A conventional dial telephone 70, having a handset 71, a cradle 72, a pushbutton 73 and a dial 74, is adapted to cooperate with a pulser which supplies DC. voltage or pulses alternately to the two halves of the motor coil through the printed leads 29, 30, 31.

The push-button 73 operates a double-pole switch 73a by opening the switch when the handset 71 is removed from the cradle 72 and closing the switch when the handset is returned to the cradle. When the dial 74 is conventionally rotated clockwise to select a number on the dial, it closes contacts 78 of switch 74a and consequently completes the circuit to the printed circuit homing leads 27, 28. When the dial returns to its starting position, it opens contacts 78 of switch 74a and closes contacts 77 to supply power to the pulser 75 and the motor 13 for a predeterminml number of pulses, equal to the dial number selected. When the handset is returned to the cradle, it causes pushbutton 73 to close switch 73a and thus complete the circuit to the printed circuit homing leads 27, 28 and also to connect the step-through contact 24 to the printed homing circuit 23.

The following sequence of events occurs when a two digit number, 67 for example, is dialed. The handset 71 is removed from the cradle 72, allowing pushbutton 73 to be projected to open switch 73a. The number 6 is dialed on the dial 74 by rotating it clockwise. Initiation of the clockwise rotation causes switch 74a to close contacts 78 and thus, place the battery voltage through printed circuit leads 27 and 28 into the pulser 75. Initially, before selecting the first digit, the motor will be in the first home position 20, and the brush 42a will be in the discontinuous portion of the homing circuit at the first home. Therefore, when the first digit is selected by a clockwise rotation of the dial, no movement of the motor will ensue.

, During the return of the dial in the counterclockwise direction to its reset position, the motor 13 will be directly energized by the pulser 75 alternately connecting one side of the D.C. source to the leads 30, 31 for six pulses, the number selected. The direct energization of the motor 13 through contacts 77 of switch 74a and the pulser 75 for six pulses will index the rotary switch arm from the first home position to the circuit branch which, of

course, in this example represents the selected digit 6.

Upon dialing the second selected digit 7, initial movement of the dial in the clockwise direction will cause switch 74a, through contacts 78, to place the homing circuit, once again, in series with the pulser '75 to drive the motor toward its second home position 21. The brush 42a and the brush 42 will maintain the circuit between the printed homing circuit 23 and the slip ring 25, causing the motor 13 to be continually pulsed and indexed until the brush 42a. reaches the substantial discontinuity at the second home position 21.

When the dial returns in the counterclockwise direction to its reset position, the pulser 75, in series with the switch 74a through the terminals '77, directly energizes the motor with seven pulses. This advances the rotary switch arm 105 to the circuit branch q representing the selected number 7.

Upon completion of the telephone call, pushbutton 73 will be depressed by the return of the handset 71 to the cradle 72 causing the switch 73a to close and to short the step-through contact 24 to the homing circuit 23. At the same time, the pulser 75 is actuated for a sufiicient number of pulses to home the arm from any position. The motor 13 will then be driven through the homing circuit 23 and step-through contact 24, since the return of the handset to the cradle additionally causes switch 73a to switch the. homing circuit into series with the motor 13 through the pulser 75. The motor will then be encrgized through the homing circuit 23 and the slip ring 25 until the brush 42a reaches the discontinuity at the first home position 20 and deenergizes the motor while it is in the first home position.

The novel step-through contact is utilized in one-digit selections. For example, had the number 6 alone, rather than 67, been selected, the motor would normally home to the second home position 21 upon the return of the handset to the cradle, if the homing were to be controlled through the printed circuit 23 alone. However, by shorting the pulsing input from the homing circuit 23 to the step-through contact 24, upon closure of the switch 73a by the returned handset, the motor is pulsed even While in the discontinuity of the second home position to allow the brush 42a and the brush arm 15 to step-through the discontinuity and return to the first home position.

The advantage of this circuitry, of course, is that the rotary switch unit will always home to the first home position upon the completion of a telephone call, irrespective of the number of digits dialed, yet the unit may also home to the second home position when a two-digit numher is to be dialed.

The novel concept of disengaging a resilient switch hand from physical contact with a series of switch contacts by the action of an electromagnetic clutch during the period of switch selection and subsequently re-engaging the switch hand to short out the non-selected contacts has yielded many advantages. Among the greatest of these is the reduction of mechanical and electrical loads on the motor during stepping, which reduction has allowed the use of an extremely compact, low-torque stepper motor for achieving switch selection. A most obvious advantage is the improved mode of rotary switching which eliminates repetitive makes-and-breaks during switch selection and results in a single make-'and-break for each switch selection. The mode of switching also provides a new and improved switch for instantly shorting out all of the non-selected switch contacts while simultaneously connecting an electrical source to the selected contact.

The new and improved homing circuits, as outlined hereinabove, provide simplified and efiicient circuitry to accommodate multiple homing of a stepper motor. Use of the auxiliary step-through contact allows a stepper motor to bypass or travel through intermediate home positions in a most expedient manner to return to a primary home position.

Thus, it is to be appreciated that the rotary stepping switch unit of the present invention accomplishes multiple switching with minimum power requirements by means of a resilient, rotary switch arm cooperating with a clutch operated, resilient switch hand to reduce the motor loads, and the uni-t also provides a new and improved multiple homing system.

Although the present invention has been described with reference to a specific, preferred embodiment, it Should be understood that the disclosure has been made only by Way of example and that certain changes in details of construction and arrangement of the elements may be made without departing from the spirit and scope of the invention .as hereinafter claimed.

\Ve claim:

1. A rotary stepping switch unit comprising:

(a) a stepper motor having a rotor shaft and means selectively indexing said shaft upon predetermined electrical inputs to the motor; k

(b) 'a switch deck maintained in a fixed relationship with said stepper motor;

(c) a plurality of switch contacts disposed in a substantially circular pattern on said switch deck;

(d) a slip ring located on said switch deck concentrically within the pattern of said switch contacts;

(e) a rotary switch arm cooperating with and indexed by said rotor shaft;

(f) said switch arm being formed from a resilient, conductive material, said arm electrically and selectively connecting said switch contacts with said slip ring;

g) said switch arm being normally supported free from contact with said switch contacts;

(h) a switch hand movable toward and away from said switch contacts;

(i) a plurality of spring fingers carried by said switch hand;

(j) said spring fingers selectively cooperating with said switch contactsto connect said contacts to a first electrical source;

(k) said spring fingers selectively cooperating with said switch arm to urge said switch arm into contact with a selected switch contact; and

(l) insulating means precluding electrical conduction between said switch arm and said switch fingers.

2. A switch unit according to claim 1, which includes:

(a) a clutch means for selectively moving said switch hand toward and away from said switch deck.

3. A switch unit according to claim 2, in which:

(a) said clutch means comprises a spring-biased electromagnetic clutch;

(b) said clutch normally spring-biases Said spring fingers away from said switch deck; and

(c) upon energization said clutch moves said spring fingers toward said switch deck.

4. A rotary stepping switch comprising:

(a) a stepper motor having a projecting rotor shaft;

(b) a rotary switch arm cooperating with said rotor shaft and being selectively indexed therewith about a predetermined axis of rotation;

(c) a plurality of first switch contact means disposed in a primary circular pattern about the axis of rotation of said switch arm;

(d) at least one secondary pattern of second switch contact means dipsosed concentrically with said primary pattern;

(c) said rotary switch arm having a conductive portion;

(f) said conductive portion registering selectively with at least two of said concentrically disposed switch contact means;

(g) a switch hand means selectively cooperating with said switch arm;

(h) said switch hand means being movable toward 1 and away from said switch contact means; and

(i) said SWitCh hand means selectively urging said switch arm conductive portion into contact with said at least two switch contact means. 5. A rotary stepping switch according to claim 4, in

which:

(a) said switch hand means is formed of a conductive material;

(b) said switch hand means includes a plurality of resilient fingers;

(c) said fingers selectively urge said switch arm conductive portion into contact with said at least two switch contact means;

(d) whereby said fingers connect a predetermined number of said switch contact means .to an electrical source; and

(e) an insulating means precludes electrical conduction between said switch hand and said conductive portion of said switch arm.

6. A stepping switch according to claim 4, in which:

(a) said switch hand is selectively movable toward said switch arm by an electromagnetic clutch means.

7. A stepping switch according to claim 4, in which:

(a) said switch arm conductive portion is normally maintained in contact with said primary switch contact means.

8. A stepping switch according to claim 6, in which:

(a) said electromagnetic clutch means is energized independently and mutually exclusively of said stepper motor.

9. A rotary stepping switch comprising:

(a) a stepper motor having a rotor shaft;

(b) a rotary switch arm indexed in predetermined angular increments by said rotor shaft;

() .a switch deck having a printed slip ring thereupon;

(d) said rotary switch arm having :an axis of rotation passing through the center of said slip ring;

(e) a plurality of printed switch contacts disposed concentrically with said slip ring;

(f) said rotary switch arm having a conductive pole portion which is selectively radially registered with said switch contacts and sectors of said slip ring;

(g) a switch hand having a plurality of resilient spring fingers;

(11) said switch hand being formed of electrically conductive material;

(i) said spring fingers being selectively moved into :and

out of contact with each of said switch contacts;

(i) an armature cooperating with said switch hand and being urged away from said switch contacts by a spring means;

(k) an electromagnetic means selectively moving said armature into engagement with said switch contact; and

(1) .an insulator carried by said pole portion of said switch arm to preclude electrical conduct-ion between said arm and said switch hand;

(in) whereby upon :a selective energization of said motor, said switch arm is indexed into registry with a selected switch contact, and upon a subsequent energization of said electromagnetic means, said switch hand urges said pole portion into contact with said selected switch contact and said slip ring to complete a circuit therebetween, while said switch fingers contact the non-selected switch contacts.

10. A rotary stepping switch comprising (a) a flexible rotary switch arm mounted for rotation about a predetermined axis,

('b) a motor; means interconnecting said motor and switch arm for rotating said arm about said axis to predetermined radial posit-ions,

(c) means supporting a plurality of contacts in a spaced axial relation with said switch arm in each of said radial positions, said axial spacing thereby accommodating free rotation of said switch arm,

(d) electromagnetic means selectively operable upon predetermined positioning of said switch arm in registry with one of said contacts, and

(e) finger means actuated by said electromagnetic means to flex said switch arm axially into physical engagement with said contact means to complete a predetermined electrical circuit,

(f) said finger means normally being maintained in spaced relation with said switch arm to accommodate its free rotation.

References Cited by the Examiner UNITED STATES PATENTS 1,543,824 6/1925 Craft.

2,199,775 5/1940 Basset 200-92 2,200,989 5/ 1940 Lennox et al ZOO-92 2,537,944 1/1951 Colgan ZOO-92 X 2,710,896 6/1955 Graybill et .al. 200- 2,823,285 2/1958 Stone 200-105 X 2,894,096 7/1959 Schacht 200105 BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner. 

10. A ROTARY STEPPING SWITCH COMPRISING (A) A FLEXIBLE ROTARY SWITCH ARM MOUNTED FOR ROTATION ABOUT A PREDETERMINED AXIS, (B) A MOTOR; MEANS INTERCONNECTING SAID MOTOR AND SWITCH ARM FOR ROTATING SAID ARM ABOUT SAID AXIS TO PREDETERMINED RADIAL POSITIONS, (C) MEANS SUPPORTING A PLURALITY OF CONTACTS IN A SPACED AXIAL RELATION WITH SAID SWITCH ARM IN EACH OF SAID RADIAL POSITIONS, SAID AXIAL SPACING THEREBY ACCOMMODATING FREE ROTATION OF SAID SWITCH ARM, (D) ELECTROMAGNETIC MEANS SELECTIVELY OPERABLE UPON 